Section 250.720 - When and how must I secure a well?(a) Whenever you interrupt operations, you must notify the District Manager. Before moving off the well, you must have two independent barriers installed, at least one of which must be a mechanical barrier, as approved by the District Manager. You must install the barriers at appropriate depths within a properly cemented casing string or liner. Before removing a subsea BOP stack or surface BOP stack on a mudline suspension well, you must conduct a negative pressure test in accordance with § 250.721 . (1) The events that would cause you to interrupt operations and notify the District Manager include, but are not limited to, the following: (i) Evacuation of the rig crew;(ii) Inability to keep the rig on location;(iii) Repair to major rig or well-control equipment;(iv) Observed flow outside the well's casing (e.g., shallow water flow or bubbling); or(v) Impending National Weather Service-named tropical storm or hurricane.(2) The District Manager may approve alternate procedures or barriers, in accordance with § 250.141 , if you do not have time to install the required barriers or if special circumstances occur.(3) If you unlatch the BOP or LMRP: (i) Upon relatch of the BOP, you must test according to § 250.734(b)(2) , or(ii) Upon relatch of the LMRP, you must test according to § 250.734(b)(3) ; and(iii) You must submit a revised permit with a written statement from an independent third party certifying that the previous certification under § 250.731(c) remains valid and receive District Manager approval before resuming operations.(b) Before you displace kill-weight fluid from the wellbore and/or riser, thereby creating an underbalanced state, you must obtain approval from the District Manager. To obtain approval, you must submit with your APD or APM your reasons for displacing the kill-weight fluid and provide detailed step-by-step written procedures describing how you will safely displace these fluids. The step-by-step displacement procedures must address the following: (1) Number and type of independent barriers, as described in § 250.420(b)(3) , that are in place for each flow path that requires such barriers;(2) Tests you will conduct to ensure integrity of independent barriers;(3) BOP procedures you will use while displacing kill-weight fluids; and(4) Procedures you will use to monitor the volumes and rates of fluids entering and leaving the wellbore.(c) For Arctic OCS exploratory drilling operations, in addition to the requirements of paragraphs (a) and (b) of this section:(1) If you move your drilling rig off a well prior to completion or permanent abandonment, you must ensure that any equipment left on, near, or in a wellbore that has penetrated below the surface casing is positioned in a manner to: (i) Protect the well head; and(ii) Prevent or minimize the likelihood of compromising the down-hole integrity of the well or the effectiveness of the well plugs.(2) In areas of ice scour you must use a well mudline cellar or an equivalent means of minimizing the risk of damage to the well head and wellbore. BSEE may approve an equivalent means that will meet or exceed the level of safety and environmental protection provided by a mudline cellar if the operator can show that utilizing a mudline cellar would compromise the stability of the rig, impede access to the well head during a well control event, or otherwise create operational risks.(d) You must have the equipment used solely for intervention operations (e.g., tree interface tools) identified, readily available, properly maintained, and available for BSEE inspection upon request. This equipment is required for subsea completed wells with a tree installed, that meet the following conditions:(1) Have a shut-in tubing pressure that is greater than the hydrostatic pressure of the water column, or(2) Are not capable of having the annulus monitored. 81 FR 26022 , Apr. 29, 2016, as amended at 81 FR 46563 , July 15, 2016; 84 FR 21976 , May 15, 2019 81 FR 26022 , 7/28/2016; 81 FR 46561 , 9/13/2016; 84 FR 21976 , 7/15/2019